Manufacturing processes often require that fluids be repeatably dispensed in exact amounts. For example, production of an integrated electrical circuit can include pumping a photoresist fluid onto a suitable substrate surface, such as a metal-coated silicon wafer, which is then treated by a photolithographic process to form a selectively deposited protective mask. Portions of the wafer not protected by the protective mask are then etched, such as by chemical etching, to produce the integrated electrical circuit.
However, newer processes often require that the amount and rate of photoresist fluid disposed onto the substrate surface generally must be precise. Deposition of an uneven coating on a wafer surface, for example, can cause defects in the protective mask formed and consequent short circuiting of the resultant integrated circuit. Gas bubbles and particulates, such as gel particulates, dust and crystals within the photoresist fluid, can also cause defects in the protective mask. For example, operation of pumps to dispense photoresist fluid can reduce the photoresist fluid pressure in an amount sufficient to cause gas bubbles to form in the fluid. The bubbles can then be deposited onto the substrate surface, thereby causing defects in the protective mask subsequently formed from the photoresist fluid.
One method of dispensing a photoresist fluid on a substrate includes employing a positive displacement diaphragm pump to direct the photoresist fluid through a filter onto the substrate. However, gas bubbles often accumulate and become trapped in the pump and in the filter. Such gas bubbles can significantly diminish the quality of the protective mask formed on the substrate by becoming compressed while fluid is dispensed from the pump onto the substrate. For example, compression of gas bubbles in the pump or in the filter can significantly reduce the accuracy of the amount of fluid distributed by the pump onto the substrate by significantly diminishing the flow rate of photoresist fluid as it is dispensed onto the substrate. Diminished flow rate from the pump and filter, in turn, can cause defects in the photoresist mask formed on the substrate.
One example of such a system for dispensing fluid, is disclosed in U.S. Pat. No. 4,950,134, wherein a diaphragm is actuated by displacing a hydraulic fluid with a piston. The hydraulic fluid is sealed between the piston and the diaphragm by a sealing ring at the piston. However, the sealing ring typically will wear during movement of the piston, ultimately leading to failure of the pump or leakage of the hydraulic fluid and consequent variability or inaccuracy of the amount of fluid dispensed from the pump. Also, gas trapped within the system or within a filter through which the fluid is pumped can cause the amount of fluid dispensed to vary significantly.
Therefore, a need exists for a new system and method of filtering and dispensing fluids which overcome or minimize the above-mentioned problems.